The present invention generally relates to broadband communications. More specifically, the present invention relates to a method and system for managing bandwidth in content distribution systems.
Traditional content distribution systems, such as, digital cable, satellite, and terrestrial broadcast systems, provide content programs (e.g., video, audio and data) over a large number of RF channels. Each RF channel may contain multiple content programs, with any given content program being delivered entirely through a single RF channel.
For a conventional cable system, downstream signals of such a system are traditionally divided into evenly spaced RF channels each having a specific frequency. This specific frequency is six (6) MHz in North America and six and seven/eighths (6 ⅞) MHz outside of North America. Each RF channel has its own content head end equipment to handle transmission of one or more content programs. FIG. 1 is a simplified high-level block diagram of a typical content head end 10. As shown in FIG. 1, each content program or source is fed into a sequential configuration including a modulator 12, a digital-to-analog converter 14 and a frequency converter 16. Furthermore, at the customer premises end, each 6-MHz RF channel requires its own analog tuner and demodulator in order to receive the content programs being transmitted. A customer or end user selects a content program via a remote control or other device. To select a particular content program, an analog tuner is set to output only the RF channel containing the content program of interest. A channel demodulator demodulates the signals received by the analog tuner. The demodulated signals representing the content program is then sent to an end user unit which may be a video display or recording device, such as a television, VCR, or data network devices, such as, computers.
One limitation associated with the foregoing system is that the system has a relatively narrow bandwidth. As mentioned above, each RF channel is limited to a frequency bandwidth of 6 MHz. If a content program that is sent to a particular RF channel has a large amount of information, it will take longer to send the entire content program because the RF channel carrying it has limited bandwidth. For example, the typical digital bandwidth for a conventional cable system is limited to about 30-40 Mbps. High quality digital video requires about five (5) GBytes (40 Gbits) of digital content. Downloading such a file can take more than fifteen (15) minutes.
To increase the bandwidth of each RF channel, the frequency of the RF channel may be extended to higher frequencies, such as, 12-MHz and 24-MHz. This increase in RF channel bandwidth, however, only has limited success due to incompatibility with legacy systems, such as, existing customer premises equipment. There are a large number of legacy systems that are still currently in use, most of which are unable to handle or accommodate an increase in RF channel bandwidth. For example, an analog tuner and demodulator in a digital set top box that is designed to handle a 6-MHz RF channel is unable to select and demodulate a 12-MHz or 24 MHz RF channel.
Another limitation associated with the foregoing system is that the system does not efficiently utilize the available bandwidth. In digital systems, content programs are divided into packets of information which are sent over RF channels, each of which has a limited amount of bandwidth. The amount of RF channel bandwidth required to send the packets of a particular content program depends on the amount of information in that content program. Furthermore, due to the physical separation of the RF channels, the system is unable to utilize the full available bandwidth. For example, assume an RF channel has a total bandwidth of 20 Mbps and one or more digital video programs each requiring a bandwidth of 3-4 Mbps. After accommodating multiple digital video programs, the RF channel typcially has 1-2 Mbps remaining in its total bandwidth. This remaining bandwidth, however, is usually unusable because it is not sufficient to support at least one single digital video program.
In addition, to function properly, traditional cable systems insert null packets into an RF channel if the collective number of packets for the content programs being transmitted does not fill the RF channel to capacity, or alternatively, the remaining capacity is not sufficient to transmit a content program. Such null packets can be filled with arbitrary bits, such as, pseudo random information. For example, if two (2) content programs of two (2) units each were carried by an RF channel having enough bandwidth to carry five (5) units of content programs, one (1) unit of null packets would be inserted into the RF channel for the system to operate properly. In this example, one (1) unit worth of bandwidth would in effect go unused.
Hence, it would be desirable to provide a method and system for use in connection with a content distribution system that is capable of efficiently utilizing the available bandwidth and is also compatible with existing customer premises equipment.